Disease Surveillance

Surveillance is intriguing; it involves everchanging
information and identifying trends based
on new disease data.

The purpose of public
health surveillance systems in Missouri and
nationwide is to detect changes in trends or
distribution of diseases so that investigation,
prevention, and disease control can be initiated in
the community. With this new information,
prompt and more effective action can be taken.

Communicable, environmental and occupational
diseases are tracked at the local level by the local
public health agency and also at the state level by
DHSS. Disease-specific information comes from
schools, hospitals, physicians, nurses,
laboratories and others.

Local agencies have an
active system in place where they maintain
regular contact with a representative group of
local disease reporters who provide information
weekly (and when needed, daily) about diseases
that are occurring in their communities. This
enables the local agency to have a clear picture
of the occurrence of disease in their community.

Knowing what to expect in disease occurrence is
particularly important when it comes to
bioterrorism and emergency response. When
there are more reports of a specific disease than
would be expected, the agency can begin to
investigate why this is happening.

Since there are many disease-causing organisms that could be
used by terrorists to cause a large outbreak
affecting many people, knowing what is usual is
critical. If a community does not know what is
usual, it will not know what is unusual. This is the
first line of defense in implementing any
emergency plan, especially for disease
prevention.

Note: Chart was not part of original article. It was added to this webpage as a sample.

The DHSS uses disease surveillance information
to track trends statewide. Based on data
collected over many years, DHSS has calculated
for every reportable disease a trend line with
upper and lower limits. Diseases are monitored
weekly (or daily as needed) and any unusual
numbers of cases outside of what we know to be
the usual occurrence are investigated.

In some instances, one case of a disease is cause for
concern. Anthrax would be one example. In
other instances, many cases, of salmonella for
example, clustered in a community or facility
would be cause for concern.

Additionally, information is received daily from
approximately 76 "sentinel" sites that provide
data on the types of syndromes/illnesses they are
seeing in their facilities. Sentinel sites (hospitals,
physician practices, schools, large employers)
have catchment areas that include communities
that see heavy tourism, areas surrounding military
installations, major utilities, large population
centers or areas otherwise strategically significant
to allow early detection of natural and man-made
public health threats in time to minimize their
impact on public health and even save lives.

Sentinel sites provide data daily on how many
people are seen with respiratory illness,
influenza-like illness, gastrointestinal illness,
unusual bleeding, headaches, rashes, fevers or
chemical exposures. Because these symptoms/
illnesses could indicate possible biological,
chemical or radiological exposures (potential acts
of terrorism), being able to identify whether the
number of instances of these symptoms is
unusually high and the area where they are
occurring is critical to early intervention.

All disease surveillance, whether it is active,
passive or sentinel, provides data that local
agencies and the department can use to develop
a comprehensive picture of what is happening. It
is one concrete method of constantly monitoring
the health of the public, so an unusual disease is
identified quickly or an unusual number of cases
of a disease are known quickly.

Timing is everything with diseases - finding them early
before many are ill and implementing prevention
and control measures to keep others from
becoming ill is what surveillance is all about.

Article by Lyn Konstant, Ph.D., Office of Surveillance
Reprinted with author's permission, from the Missouri Department of Health and Senior Service's June 2003 "Public Health Preparedness and Response UPDATE".